The present invention concerns optimal placement of circuit components on an integrated circuit so as to minimize the total circuit area.
An integrated circuit is generally divided into circuit components. Each of the circuit components occupies a fixed area when placed on the integrated circuit. Further, each circuit component is connected to other circuit components through connection lines. These connection lines have a measurable width and take up space on the integrated circuit which is directly proportional to their length.
When selecting locations on the integrated circuit in which to place the circuit components, it is desirable to select locations so that the area on the integrated circuit is optimally utilized. Optimal placement of circuit components occurs when the dead space, that is area between circuit components which is not utilized by circuit components, is minimized, and when the total length of connections lines is minimized.
Often a bottom-up slicing tree is used to accomplish the optimum placement. This method starts with a list of the circuit components. For every possible pairing of the circuit components a total cost is calculated. In the prior art, this is typically done by calculating the amount of dead space created by the pairing to generate a first cost, and by determining the number of connection lines between the two circuits to generate a second cost. The first cost and the second cost are each weighted a fixed amount before being added together to produce the total cost. The amount of weighting is selected based on empirical data.
The pairing which produces the lowest total cost is merged into a new circuit component. The new circuit component is added to the list and the two components which form the new component are removed from the list. Again, for every possible pairing of the circuit components on the list a total cost is calculated. The pairing with the lowest total cost is merged into a new component. The process is repeated until only a single circuit component remains on the list.
When two components are merged into a new circuit component, they are assigned a vertical or horizontal orientation. Also, the order in which the components are merged is recorded. The orientation and order of merging are used to produce a merge tree. The merge tree may then be traversed to select locations within an integrated circuit for each of the circuit components.
The prior art method of calculating the total cost of each pair of components fails to take into account that the optimal weighting of the first cost and the second cost varies depending on the particular circuit components used. It is desirable to find a method to calculate the total cost of each pairing without relying upon arbitrarily selected weighting values.